Amphotericin has served as the gold standard for treatment of life-threatening systemic fungal infections for more than half a century, and resistance to this antibiotic remains exceptionally rare. However, amphotericin is also highly toxic, and thus the effective treatment of systemic fungal infections is all too often precluded, nt by a lack of efficacy, but by dose-limiting side effects. Because systemic fungal infections represent a major and growing threat to human health worldwide, a less toxic but equally effective amphotericin derivative stands to have a major impact. Recently, in contrast to the widely accepted channel model, we discovered that amphotericin primarily exerts its activity against yeast and human cells by simply binding ergosterol and cholesterol, respectively. Thus, rather than trying to promote the self-assembly of multimeric ion channels selectively in yeast vs. human cells, efforts toward an improved therapeutic index can now focus directly on the much simpler goal of more selectively binding ergosterol vs. cholesterol. To maximally enable the rational pursuit of this objective, we herein propose to harness the power of organic synthesis to systematically characterize the key structure-function relationships that underlie thi very rare type of small molecule-small molecule interaction. Collectively, these studies will substantially illuminate the fundamental underpinnings of AmB/sterol interactions that are central to the mechanism of action of this clinically vital antifungal agent, generate promising candidates for further development as antifungal agents with an improved therapeutic index, drive the continued development of a highly efficient and flexible building block-based platform for small molecule synthesis, as well as advance site-selective functionalizations as a powerful strategy for accessing targeted derivatives of complex natural products.